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package org.openjdk.jmh.samples;


import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;


public class JMHSample_01_HelloWorld {


    /*

     * This is our first benchmark method.

     *

     * JMH works as follows: users annotate the methods with @Benchmark, and

     * then JMH produces the generated code to run this particular benchmark as

     * reliably as possible. In general one might think about @Benchmark methods

     * as the benchmark "payload", the things we want to measure. The

     * surrounding infrastructure is provided by the harness itself.

     *

     * Read the Javadoc for @Benchmark annotation for complete semantics and

     * restrictions. At this point we only note that the methods names are

     * non-essential, and it only matters that the methods are marked with

     * @Benchmark. You can have multiple benchmark methods within the same

     * class.

     *

     * Note: if the benchmark method never finishes, then JMH run never finishes

     * as well. If you throw an exception from the method body the JMH run ends

     * abruptly for this benchmark and JMH will run the next benchmark down the

     * list.

     *

     * Although this benchmark measures "nothing" it is a good showcase for the

     * overheads the infrastructure bear on the code you measure in the method.

     * There are no magical infrastructures which incur no overhead, and it is

     * important to know what are the infra overheads you are dealing with. You

     * might find this thought unfolded in future examples by having the

     * "baseline" measurements to compare against.

     */


    @Benchmark

    public void wellHelloThere() {

        // this method was intentionally left blank.

    }


    /*

     * ============================== HOW TO RUN THIS TEST: ====================================

     *

     * You are expected to see the run with large number of iterations, and

     * very large throughput numbers. You can see that as the estimate of the

     * harness overheads per method call. In most of our measurements, it is

     * down to several cycles per call.

     *

     * a) Via command-line:

     *    $ mvn clean install

     *    $ java -jar target/benchmarks.jar JMHSample_01

     *

     * JMH generates self-contained JARs, bundling JMH together with it.

     * The runtime options for the JMH are available with "-h":

     *    $ java -jar target/benchmarks.jar -h

     *

     * b) Via the Java API:

     *    (see the JMH homepage for possible caveats when running from IDE:

     *      http://openjdk.java.net/projects/code-tools/jmh/)

     */


    public static void main(String[] args) throws RunnerException {

        Options opt = new OptionsBuilder()

                .include(JMHSample_01_HelloWorld.class.getSimpleName())

                .forks(1)

                .build();


        new Runner(opt).run();

    }

 //这里精简一下simple的代码，使用 @Benchmark 来标记需要基准测试的方法，然后需要写一个main方法来启动基准测试。
}